Oscillating pumps utilizing leaf-type check valves to move fluids through a pumping chamber are known in the art. For example, in one type of pump, an elastomeric leaf valve was formed as part of the impeller with the leaves and stem of the valve being attached internally of the elastomeric pump impeller. Then during the manufacturing process the valve leaves were cut free of the impeller to be operable therein. However, such a system provided inconsistent and inefficient pump performance because as the pressure caused the valve leaves to deform slightly during pump operation, the leaves did not always seal properly against the irregular surface of the impeller from which they were severed.
Other efforts to provide more consistent valve performance have likewise been deficient. For example, attempts were made to mold a one-piece leaf valve with its valve stem being part of a tubular elastomeric retainer which was snapped into a recess in the pump impeller. However, the inherent flexible nature of the elastomeric retainer, being made of the same material as the leaf portion of the valve, was not strong enough to resist collapse of the impeller, caused by the high internal vacuum of the pump. Further, the retainer could thereby easily work its way out of the recess in the impeller. Finally, the seal between the valve leaves and the flexible impeller was still capable of failure and inconsistent performance.